Our current research is intended to demonstrate the statistical nature of the distribution of nucleosomes in chromatin. The distinguishing feature of any statistical phenomenon is the occurrence of fluctuations. In the case of chromatin, what fluctuates is the number of nucleosomes on a given length of DNA. The computations mentioned above show that fluctuations are most pronounced for certain critical lengths of DNA. Experiments in progress are designed to count the number of nucleosomes on these critical lengths of DNA. The experiments involve restriction endonuclease digestion of chromatin in Drosophila melanogaster cell nuclei. The resulting chromatin fragments are separated by sedimentation in a sucrose gradient. DNA from each fraction of the gradient is subjected to gel electrophoresis, transferred to paper, and hybridized with 32P-labeled cloned segments from the Drosophila genome. Autoradiography reveals the distance of migration of any particular restriction fragment in the sucrose gradient and, thus, the number of nucleosomes associated with it. Work done to date has demonstrated the feasibility of this approach. It remains to collect sufficient data to determine whether the fluctuations expected from a statistical distribution of nucleosomes actually occur. (K)